Demand for integrated circuits (ICs) in portable electronic applications has motivated greater levels of semiconductor device integration. Many advanced semiconductor devices in development leverage non-silicon semiconductor materials, a subset of which have wurtzite crystallinity. Exemplary wurtzite materials include AgI, ZnO, CdS, CdSe, α-SiC, BN, GaN, AlN, the last two of which may be grouped together as being in the III-N material system. The III-N material system shows particular promise for high voltage and high frequency applications like power management ICs and RF power amplifiers. III-N heterostructure field effect transistors (HFET), such as high electron mobility transistors (HEMT) and metal oxide semiconductor (MOS) HEMT, employ a semiconductor heterostructure with one or more heterojunction, for example at an interface of a GaN semiconductor and another III-N semiconductor alloy, such as AlGaN or AlInN. GaN-based HFET devices benefit from a relatively wide bandgap (˜3.4 eV), enabling higher breakdown voltages than Si-based MOSFETs, as well as high carrier mobility. The III-N material system is also useful for photonics (e.g., LEDs), photovoltaics, and sensors, one or more of which may be useful to integrate into an electronic device platform.
Multi-chip integration approaches have been employed to integrate silicon-based devices with those based on wurtzite semiconductor materials. These multi-chip approaches have scaling and performance limitations. Monolithic integration of silicon-based devices (e.g., CMOS field effect transistors) with devices utilizing wurtzite material systems is a challenge due to a large lattice mismatch (e.g., ˜41% between GaN and Si) and a large thermal expansion coefficient mismatch (e.g., ˜116% between Si and GaN). These mismatches can result in a great number of defects in the wurtzite semiconductor thin films epitaxially grown on silicon substrates. Without an ability to control propagation of defects, regions of sufficiently low defect density may not available to form highly functional semiconductor devices. One technique for monolithic integration relies on thick buffer layers, for example of 3-10 microns, or more. Such thick buffers however are expensive and complicate silicon CMOS integration. Structures and techniques to manage defect propagation in wurtzite material systems heteroepitaxially formed on CMOS-compatible substrates without thick buffers are therefore advantageous.